With recent performance improvements, the electrical system of an automobile is wired in a number of sections such as those of various control circuits requiring a high reliability. On the other hand, a lightweight automobile is increasingly required to save energy.
In general, a wire conductor for wiring an automobile is mainly made of a stranded wire which is obtained by braiding annealed copper wires defined under JIS C 3102 or wires plated with tin. Such a stranded wire is concentrically coated with an insulating material such as vinyl chloride, bridged vinyl or bridged polyethylene, to form a wire.
In automobile wiring circuits, the number of signal current circuits for control purposes etc. in particular, has increased in recent years. A wire for such circuits is formed by a conductor having a diameter is in excess of an electrically required level for maintaining the necessary mechanical strength, in spite of sufficient current carrying capacity.
In order to reduce the weight of such a wire, an attempt has been made to make its conductor of aluminum including aluminum alloy.
In general, however, aluminum is so inferior in strength that it is necessary to increase the outer diameter of the conductor or the number of stranded wires, in order to attain sufficient strength. Consequently, the amount of the insulating material is increased which in turn requires a large space for the wiring. Thus, the weight of the wire cannot be sufficiently reduced and the cost for the insulating material is increased.